Bound Columns In Forms And Resetting Values?

I have a form for student attendance that is bound to a query and stores a temporary value for ClassesAttended in a StudentEnrollment table as faculty enters the attendance. They then run an append query to write the temporary records to a StudentAttendance table. Because the ClassesAttended field is bound, when the form is opened, it recalls the last number entered for that student in that class as entered by the faculty the last time attendance was updated. I tried leaving the field unbound, but the first value enter into the first record of the form is updated automatically to all subsequent records.

Is there a way to change the properities, use code, etc. to assigne a null or 0 to the ClassesAttended field when the form opens, without the first updated record to propagate through the reaming records?